Chemical-Mechanical Planarizing (CMP) processes are often used for forming a flat surface on a semiconductor substrate in the manufacture of electronic devices. CMP processes generally remove material from a substrate surface to create a highly planar surface. A variety of planarizing machines have been developed to carry out such CMP processes.
Planarizing machines for use in CMP processing generally fall into two categories: web-format and fixed-pad format. In each case, a planarizing pad and a planarizing solution are combined to define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of a substrate. The planarizing pad may be of a fixed-abrasive or non-abrasive type. With a fixed-abrasive pad type, abrasive particles are fixedly bonded to a suspension material. Furthermore, the planarizing solution used with a fixed-abrasive pad type is typically a “clean” solution, i.e., substantially devoid of abrasive particles as such abrasive particles are fixedly distributed across a planarizing surface of the planarizing pad. With a non-abrasive planarizing pad, no abrasive particles are associated with the pad, so the abrasive particles are introduced in the planarizing solution. Such planarizing solutions for use with non-abrasive pad types are often slurries of both abrasive particles as well as chemicals to aid removal of material from a substrate.
To planarize the substrate with the planarizing machine, the surface of the substrate is first contacted against the planarizing pad in the presence of the planarizing solution, i.e., a planarizing surface of the planarizing medium. While in contact, the substrate is then moved relative to the planarizing surface of the planarizing medium, generally through lateral, rotational, revolving or orbital movement of the substrate, the planarizing pad or both. Lateral movement is defined as movement in one direction. Rotational movement is defined as rotation about an axis located at the center point of the object in motion. Revolving movement is defined as rotation about some axis located at other than the center point of the object in motion. Orbital movement is defined as rotational or revolving movement combined with oscillation. Different types of movement may be combined, e.g., rotational movement of the substrate and rotational movement of the planarizing pad or revolving and rotational movement of the substrate against a stationary planarizing pad. As is well understood in the art, such relative movement is in a plane substantially parallel to the surface of substrate. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate.
Fixed abrasive pad types are well known in the art of semiconductor wafer processing. See, e.g., U.S. Pat. No. 5,692,950 issued Dec. 2, 1997 to Rutherford et al.; U.S. Pat. No. 5,624,303 issued Apr. 29, 1997 to Robinson; and U.S. Pat. No. 5,335,453 issued Aug. 9, 1994 to Baldy et al. Despite widespread recognition and acceptance of fixed abrasive pads in the processing of semiconductor wafers, effective planarizing solutions for use in the fixed-abrasive planarization of an advantageous barrier material and conductor, i.e., titanium nitride (TiN), are lacking. As a result, the customary processing for planarizing titanium nitride utilizes abrasive slurries with non-abrasive pad types.
One problem with CMP processing is that the planarized surface of the wafer may not be sufficiently uniform across the whole surface of the wafer. In the competitive semiconductor industry, it is also desirable to maximize the throughput of finished wafers. The uniformity of the planarized surface and maximization of throughput is a function of the effectiveness and repeatability of the planarizing solution utilized with the planarizing pad, as well as a wide array of other CMP operating parameters. While a wide variety of planarizing solutions are available, these solutions are generally specific to the composition of the material to be removed as well as the type of planarizing pad used. For obvious reasons, planarizing solutions developed for non-abrasive pad types are ill suited for use with fixed-abrasive pad types. Therefore, it would be desirable to develop effective planarizing solutions for planarization of titanium nitride on the surface of a semiconductor wafer for use in conjunction with fixed-abrasive planarizing pads.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for methods of planarizing titanium nitride using fixed-abrasive planarizing pads.